Method and apparatus for accessing the left atrial appendage

ABSTRACT

Disclosed is an apparatus for facilitating access to the left atrium, and specifically the left atrial appendage. The apparatus may comprise a sheath with first and second curved sections that facilitate location of the fossa ovalis and left atrial appendage. The apparatus may further comprise tissue piercing and dilating structures. Methods are also disclosed.

This is a continuation-in-part of U.S. patent application Ser. No.09/549,218, filed Apr. 13, 2000 now U.S. Pat. No. 6,650,923, thedisclosure of which is incorporated in its entirety herein by reference.

BACKGROUND OF THE INVENTION

The present invention relates to transseptal access systems foraccessing the left atrium from the right atrium such as by crossing thefossa ovalis.

The typical human heart includes a right ventricle, a right atrium, leftventricle and left atrium. The right atrium is in fluid communicationwith the superior vena cava and the inferior vena cava. The tricuspidvalve separates the right atrium from the right ventricle. On the innerwall of the right atrium where it is separated from the left atrium is athin walled, recessed portion, the fossa ovalis. In the heart of afetus, the fossa ovalis is open (patent foramen), permitting fetal bloodto flow between the right and left atria, bypassing the fetal lungs infavor of the placental blood flow. In most individuals, this openingcloses after birth. In as many as about 20 percent of adults an opening(the patent foramen) still remains in place of the fossa ovalis betweenthe right and left atria.

A wide variety of diagnostic and therapeutic procedures have beendeveloped in which a catheter is transluminally advanced into variouschambers and across valves of the heart. The most difficult chamber ofthe heart to access with a catheter is the left atrium. Access to theleft atrium through the pulmonary artery is not possible. Approachesfrom the left ventricle are difficult, may cause arrhythmias and maypresent difficulty in obtaining stable catheter positioning.Accordingly, the presently preferred method of accessing the left atriumis through a transseptal approach, achieved by catheterization of theright atrium with subsequent penetration of the interatrial septum. Thereduced wall thickness and location of the fossa ovalis makes it auseful access point for a transseptal access puncture.

A variety of risks are attendant to transseptal catheterization, inaddition to the risks associated with normal heart catheterization. Theprimary additional risk is that associated with inaccurateidentification and localization of the atrial septum and the fossaovalis in particular. Improper placement of the catheter tip prior tothe transseptal puncture presents the risk of puncture of tissue otherthan the interatrial septum, such as the aorta and the posterior wall ofthe right or left atrium. For this reason, catheterization isaccompanied by fluoroscopy or other visualizing techniques to assist inproperly locating the catheter tip in relation to the septum.

The objectives of left atrial access can be either diagnostic ortherapeutic. One diagnostic use is pressure measurement in the leftatrium. In the setting of an obstructed mitral valve (mitral stenosis),left atrial access allows a determination of the pressure differencebetween the left atrium and left ventricle. Left atrial access alsoallows entry into the left ventricle through the mitral valve. This isdesirable when an artificial aortic valve is in place. The advent ofaortic valve replacement with mechanical artificial valves, and theincrease in the aged population and growing longevity of that populationsubsequent to aortic valve replacement, brings a greater need toevaluate the late stage functionality of such artificial valves.

Diagnostic measurement of the left ventricular pressures are, therefore,desirable to allow evaluation of mechanical artificial aortic valvespost-replacement. It may be unsafe to cross these mechanical artificialvalves retrograde from the aorta; therefore, access to the leftventricle by the antegrade route using a transseptal puncture is thepreferred approach. Once a catheter has been placed in the left atriumusing the transseptal approach, access to the left ventricle can begained by advancing catheters across the mitral valve.

Many diagnostic indications exist for left atrial pressure measurementsin addition to evaluating the functionality of artificial mitral valves.Other diagnostic indications for accessing the left ventricle via theantegrade transseptal approach include aortic stenosis, when acardiologist is unable to pass a catheter retrograde into the leftventricle, and some disease states where the antegrade approach isconsidered preferable, such as subaortic obstruction.

Presently, the therapeutic objectives of left atrial access areprimarily two-fold. The first is mitral valvuloplasty which representsan alternative to surgical procedures to relieve obstruction of themitral valve. The second therapeutic objective is forelectrophysiological intervention in the left atrium. Catheter ablationinvolves the placement of energy (typically RF) through a catheter, intovarious locations of the heart to eradicate inappropriate electricalpathways affecting the heart function. When these locations are in theleft atrium, the catheter through which the radio frequency generator isplaced typically is itself placed with transseptal catheterization. Morerecently, therapeutic treatment of the left atrial appendage (LAA) toreduce the risk of embolic stroke has also been proposed.

Despite clinical acceptance of a wide variety of procedures whichrequire access to the left atrium, significant room for improvementremains in the actual access technique. For example, the step oflocating an appropriate site on the septum such as the fossa ovalis ishighly technique dependant and can be inaccurate. This increasesprocedure time, and creates a risk that the needle will pierce the heartwall in an unnecessary and potentially undesirable location. Thus, thereremains a need for a device and method for quickly and accuratelylocating and piercing the fossa ovalis to permit rapid and accuratetransseptal access.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided a transseptal access sheath comprising; a first curved section,and a second curved section; the first curved section having an outeredge that defines a first proximal edge point, and a first distal edgepoint, wherein the intersection between a tangent drawn to the firstcurved section at the first proximal edge point and a tangent drawn tothe first curved section at the first distal edge point, define a firstangle and a first plane; the second curved section having an outer edgethat defines a second proximal edge point, and a second distal edgepoint; wherein the intersection between a tangent drawn to the secondcurved section at the second proximal edge point and a tangent drawn tothe second curved section at the second distal edge point, define asecond angle and a second plane; wherein the first angle is within therange of about 60 to about 120 degrees; wherein the second angle iswithin the range of about 0 and about 180 degrees, more preferably about60 and about 120 degrees; and wherein the angle between the first andsecond plane is within the range of about 60 and about 120 degrees.

In accordance with another aspect of the present invention, there isprovided a transseptal access sheath comprising; a first curved section,and a second curved section; wherein the first curved section is shapedto abut the interior wall of the right atrium substantially opposite thefossa ovalis while directing the distal tip toward the fossa ovalis;and, wherein the second curved section is shaped to facilitate locationand access of a desired region of the LAA.

In accordance with another aspect of the present invention, there isprovided a transseptal access system comprising a sheath, a dilator anda needle; wherein the sheath comprises; a first curved section, and asecond curved section; the first curved section having an outer edgethat defines a first proximal edge point, and a first distal edge point,wherein the intersection between a tangent drawn to the first curvedsection at the first proximal edge point and a tangent drawn to thefirst curved section at the first distal edge point, define a firstangle and a first plane; the second curved section having an outer edgethat defines a second proximal edge point, and a second distal edgepoint wherein the intersection between a tangent drawn to the secondcurved section at the second proximal edge point and a tangent drawn tothe second curved section at the second distal edge point, define asecond angle and a second plane; wherein the first angle is within therange of about 90 degrees; wherein the second angle is within the rangeof about 90 degrees; and wherein the angle between the first and secondplane is within the range of about 90 degrees.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational schematic view of a transseptal accesssystem in accordance with the present invention.

FIG. 2 is a cross-sectional view taken along the line 2—2 in FIG. 1.

FIG. 3 is an enlarged perspective view of the distal end of thetransseptal access system of FIG. 1.

FIG. 4 is a schematic cross-sectional view of a portion of the heart,showing a transseptal access catheter of the present invention withinthe right atrium.

FIG. 5 is a cross-sectional view as in FIG. 4, with the guidewirepositioned in the superior vena cava.

FIG. 6 is a cross-sectional view as in FIG. 4, with the transseptalaccess catheter positioned against the wall of the superior vena cava.

FIG. 7 is a cross-sectional view as in FIG. 4, with the access catheterpositioned against the fossa ovalis.

FIG. 8 is a cross-sectional view as in FIG. 4, showing tissue distentionor “tenting” as the needle punctures the fossa ovalis.

FIG. 9 is a cross-sectional view as in FIG. 8, showing tissue distentionas the dilator is advanced through the fossa ovalis.

FIG. 10 is a cross-sectional view as in FIG. 9, illustrating the sheath,which has been advanced over the dilator and through the septum.

FIG. 11 is a cross-sectional view as in FIG. 10, with the dilatorremoved, leaving the sheath in place across the fossa ovalis.

FIGS. 12 and 13 are perspective schematic views of a transseptal accesssheath in accordance with the present invention.

FIGS. 14A–C are perspective views of vents in the transseptal accesssheath.

FIGS. 15A–C are side views of a dilator in accordance with oneembodiment of the present invention.

FIGS. 16A–C are side views of various dilators in accordance withfurther embodiments of the present invention.

FIGS. 17A–C are side views of the jacket in accordance with oneembodiment of the present invention.

FIG. 18 is a side view of the transseptal access sheath in accordancewith one embodiment of the present invention.

FIG. 19 is a side view of the transseptal access sheath in accordancewith one embodiment of the present invention.

FIGS. 20A and 20B are side views of the needle in accordance with oneembodiment of the present invention.

FIG. 21 is a side view of the needle in accordance with one embodimentof the present invention.

FIGS. 22A–22H are side views of various needles in accordance withfurther embodiments of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is disclosed a dilator 20 in accordance withthe present invention. Dilator 20 has a proximal end 22, a distal end 24and an elongate flexible tubular body 26. The overall length of thedilator 20 depends upon the percutaneous access point and the desiredapplication. For example, lengths in the area of from about 80 cm toabout 100 cm are typical for use in percutaneous transluminal access atthe femoral vein for locating and puncturing a site on the atrial septumin the heart.

Tubular body 26 may be manufactured in accordance with any of a varietyof known techniques, for manufacturing catheters adapted to reach thecoronary arteries or chambers of the heart. For example, tubular body 26may be manufactured as an extrusion of appropriate biocompatiblepolymeric materials such as high density polyethylene,polytetrafluoroethylene (PTFE), nylons, and a variety of others whichare known in the art. Blended materials may also be used, such as HDPE(e.g., HDPE/LDPE ratios such as 50%:50%, 60%:40% and others) with fromabout 5% to about 25%, and, in one embodiment, about 20% BaSO.sub.4 forlubricity and radiopacity. Alternatively, at least a portion or all ofthe length of tubular body 26 may comprise a spring coil, solid walledhypodermic needle tubing (e.g., stainless steel, NiTi alloys) or braidedreinforced wall as is understood in the catheter and guidewire arts.

For most applications, the tubular body 26 is provided with anapproximately circular cross sectional configuration having an outsidediameter within the range of from about 0.020 inches to about 0.200inches. In accordance with one embodiment of the invention, the tubularbody 26 has an outside diameter of about 0.160 inches throughout itslength. Other lengths and diameters may be readily utilized, dependingupon the desired profile and performance characteristics.

The proximal end 22 is provided with a manifold 28, having one or moreaccess ports as in known in the art. In the illustrated embodiment,manifold 28 is provided with a core wire port 32 which may also oralternatively function as a guidewire port in an over the wireembodiment. An injection port 30 may also be provided, for injecting acontrast media, such as to confirm that the distal end 24 has traversedthe intraatrial septum. Additional access ports may be provided asneeded, depending upon the functional capabilities of the catheter.Manifold 28 may be injection molded from any of a variety of medicalgrade plastics or formed in accordance with other techniques known inthe art.

The proximal end 22, either at the manifold 28 or distally of themanifold 28 is also provided with a communication line 34 such as afiber optic bundle 35 in accordance with one aspect of the presentinvention. In one embodiment of the invention, fiber optic bundle orsignal transmitting line 35 communicates with a signal e.g. sound,light, ultrasonic or other vibration, etc.) generator and detector 37.In this embodiment of the invention, the detector 37 enables thecatheter to distinguish among solid tissue or a thick membrane, a thinmembrane such as at the fossa ovalis, and right atrial or left atrialchamber blood beyond the distal end 24 of dilator 20 as will bediscussed.

The flexible body 26 is provided with a preset bend 25, for assisting inbiasing the distal end 24 against the intraatrial septum as isunderstood in the art. Bend 25 preferably has a radius within the rangeof from about 0.5 cm to about 5 cm and, in one embodiment, about 2.5 cm.Bend 25 is centered on a point which is within the range of from about 1cm to about 10 cm proximally from distal end 24. In one embodiment, thebend 25 is centered at approximately 6 cm proximally from distal end 24.The bend 25 is defined by a proximal transition where it meets thesubstantially linear proximal portion of the dilator 20, and a distaltransition where it meets the substantially linear distal portion of thedilator 20. The angular deflection of the bend 25 is generally withinthe range of from about 30° to about 80° and, in one embodiment, isabout 50°.

Bend 25 may be provided in accordance with any of a variety oftechniques. For example, in an embodiment of tubular body 26 whichincludes a hypotube or other metal tubing, the tubular body 26 may bebent such as around a forming mandrel in excess of the elastic limit ofthe hypotube. Alternatively, an injection molded catheter body may beheat set in a predetermined bend, such as with removable flexiblemandrels extending through any interior lumen to maintain patency of thelumen around the bend. Other techniques will be known to those of skillin the art. Alternatively, the bend 25 may be formed during or afterplacement of the catheter in the heart. This may be accomplished byproviding the catheter with any of a variety of steering mechanisms,which allow a distal portion of the catheter to be inclined away fromthe axis of the normal bias of the catheter. For example, one or moreaxially moveable pull wires may extend throughout the length of thecatheter. Proximal traction on a pull wire which is secured at thedistal end of the catheter will cause a lateral defection of thecatheter.

Referring to the enlarged schematic illustration of FIG. 3, distal end24 is provided with at least one signal transmitting surface 47 and atleast one signal receiving surface 49. Transmitting surface 47 isadapted to transmit a signal from the distal end 24 of dilator 20 andgenerally in the distal direction with respect to the dilator. Receivingsurface 49 is adapted for receiving a reflected return signal travelingin a generally proximal direction with respect to the distal end 24 ofdilator 20. In one embodiment, the transmitting surface 47 comprises thedistal end of a fiber optic or fiber optic bundle, or a transparentwindow positioned at the distal end of a fiber optic or fiber opticbundle. Similarly, the receiving surface 49 comprises a distal end of areceiving fiber optic or a transparent window positioned distally of thereceiving fiber optic. In the illustrated embodiment, two transmittingsurfaces 47 and two receiving surfaces 49 are provided eachcommunicating with the spectrometer 37 via a unique communication line34.

Transmission and reception of, for example, visible light, canalternatively be accomplished though a single transparent window, andembodiments in which the transmission and reception signals arepropagated through the same fiber optic or through closely adjacentfiber optics are also contemplated. Propagation of transmission andreception signals through the same fiber optic can be accomplished suchas by the provision of a coupler at the proximal end to split thetransmission and reception signals for processing at detector 37 as willbe understood in, among others, the blood oximetry detector arts.Alternatively, one or more separate transmit surfaces 47 and receivingsurfaces 49 may be provided, and anywhere within the range of from about1 to about 12 of each transmit surface 47 and receiving surface 49 maybe provided as desired.

Signal transmitting bundle 35 thus provides communication between thetransmit surface 47 and receiving surface 49, and a detector 37 such asa spectrometer which remains outside of the patient. The constructionand use of spectrometers such as to measure RGB and other UV, visibleand IR wavelengths is well understood in the pulse oximetry art, amongothers, and will not be disclosed in detail herein. In general,transmitter/detector 37 is able to transmit multiple wavelengths oflight, which propagate beyond the transmit surface 47 and into a targetbeyond the distal end 24 of the dilator 20. Some of the transmittedlight is absorbed in the target, while other transmitted light isreflected back and received at receiving surface 49. The reflected lightis thereafter propagated to the light detector 37 for processing. Thepresent inventors have determined that the light detector 37 incombination with the dilator of the present invention can identify whenthe distal end 24 of the dilator 20 is positioned against the fossaovalis of the intraatrial septum, as opposed to other portions of theseptum or muscle wall, due to the unique characteristics of lightobserved at the fossa ovalis.

Depending upon the characteristics of the transmitted light, reflectedlight at the fossa ovalis will exhibit unique characteristics impartedby (1) light reflected at the surface of or within the fossa ovalis, (2)light reflected through the fossa ovalis by blood in the left atrium, or(3) a combination of the foregoing. The ability of an optical detectorto locate the fossa based upon light propagated through the fossa isbased upon several circumstances. The blood in the right atrium isrelatively poorly oxygenated, and therefore more blue than red. The leftatrium contains well oxygenated blood which tends to be relatively red.The fossa is thin enough to allow light to be transmitted across thefossa and into and from the left atrium while the fossa locator is stillon the right atrial side. All other areas of the septum are generallythick enough that they will not allow significant light transmissionbetween the right atrium and the left atrium. Thus, in an embodiment ofthe invention which utilizes light transmission through the fossa, thelocation of relatively red blood indicates transmission into the leftatrium which will generally only happen at the fossa.

Alternatively, the septum contains oxygenated blood and therefore has acertain level of red transmission. The fossa, however, is a thintranslucent membrane which is almost yellow. Non-oxygenated blood withinthe right atrium is relatively blue, while oxygenated blood within theleft atrium is red. Location of the fossa may thus alternatively beaccomplished by identifying the presence of a translucent, near yellowmembrane. The use of multiple wavelengths, transmission, and detectorswill allow assessment of both the near yellow color of the fossa, aswell as the red color identified through the fossa as will be apparentto those of skill in the art in view of the disclosure herein.

The method of the present invention may additionally be accomplished byproviding a light source within the left atrium. The left atrium lightsource may be provided on any of a variety of left atrium accesscatheters, as will be apparent to those of skill in the art. Lightgenerated in the left atrium, will be detectable in the right atriumeither exclusively at the fossa, or with a greatest intensity appearingat the fossa. Thus, the left atrium dilator 20 need only be providedwith light detector optics and electronics, to identify the fossa basedupon the characteristics of light received from the right atrium lightsource.

The dilator 20 is additionally provided with a tissue piercing structure42 such as a needle 44. Needle 44 preferably comprises a tubularstructure such as a stainless steel hypotube having a sharpened distalend 50. The sharpened distal end 50 of needle 44 is axially moveableadvanceable through an aperture 45 in the distal end 24 of the tubularbody 26.

In one embodiment of the invention, the needle 44 has an axial length offrom about 1 cm to about 5 cm, an inside diameter of about 0.022 inchesand an outside diameter of about 0.032 inches. Any of a variety of otherdimensions for needle 44 may also be used depending upon the desiredperformance and overall catheter dimensions. Needle 44 is connected tothe distal end 40 of a control element such as core wire 36 whichaxially moveably extends throughout the length of tubular body 26. Theproximal end 38 of the core wire 36 in the illustrated embodimentextends proximally from the core wire port 32. The needle 44 ispreferably axially moveable between a first position in which the tip 50is contained within the distal end 24 of the tubular body 26 and adistal position in which the distal tip 50 of the needle 44 is exposedbeyond the distal end of the body 26 such as for piercing the fossaovalis. Distal advancement of the proximal end 38 of core wire 36 willadvance the needle 44 from the first position to the second position aswill be appreciated in view of the disclosure herein. Alternatively, theneedle 44 and core wire 36 may be removed entirely from the dilator 20except when desired to pierce the septum.

The proximal end 38 of the core wire may be exposed beyond the proximalend of core wire port 32 as in the illustrated embodiment, such that thephysician can grasp the core wire 36 and advance it distally withoptimum tactile feedback. Alternatively, the proximal end 38 of corewire 36 may be connected to any of a wide variety of controls such as aslider switch, rotatable knob or other control attached to or adjacentthe manifold 28. Manipulation of the control can controllablyreciprocally move the needle 44 between the first and second position.

In an alternate embodiment, disclosed in FIGS. 6–10, the needle 44removably extends throughout the entire length of the dilator 20. Forthis embodiment, needle 44 may have an axial length of from about 100 cmto about 120 cm or longer, and, in one embodiment, about 110 cm.

In the illustrated embodiment, radiopaque dye can be injected throughthe central lumen 39, and through the hollow needle 44 (if present) forassessing the position of the distal end 24 of the dilator 20.Alternatively, blood may be withdrawn and analyzed for O₂ content bywell known methods. Left atrial blood will have an O₂ saturation ofgreater than 90%, whereas right atrial blood has an O₂ saturation ofless than 80%. A separate injection lumen (not illustrated) can bereadily provided if desired for a particular application. In addition,the needle 44 may be removable from the dilator 20. In thisconstruction, the dilator 20 retains its greatest flexibility such asfor advancement to the intraatrial access site. Once the distal end 24of the dilator 20 is positioned within the left atrium, the piercingstructure 42 such as needle 44 can be loaded into the proximal end 22 ofthe dilator 20 and advance distally throughout the length of the dilator20 and out a distal aperture 45. Once the piercing structure 42 haspierced the fossa ovalis or other structure, and the distal end 24 ofthe dilator 20 is advanced through the opening formed by the piercingstructure, the piercing structure 42 may be proximally retracted andremoved from the dilator, thereby leaving the central lumen fullyavailable for subsequent therapeutic or diagnostic devices or materials.

In one embodiment, illustrated in FIG. 21, the needle 44 may be providedwith a corkscrew thread or other helical structure 84, such as thosehaving substantially circular or triangular cross-sections, therebypermitting the needle 44 to penetrate the fossa ovalis 72 by rotatingwhile moving transversely through the opening. One of ordinary skill inthe art will appreciate that the size, shape and orientation of thehelical structures can be adjusted depending on the desired combinationof minimizing resistance during puncture or increasing the size opening.

Where it is desirable to increase the size of the opening created by theneedle 44, the needle may be configured to create an opening whenadvanced in the distal direction, and to enlarge the opening whenadvanced back through the fossa ovalis in the proximal direction. Thismay be accomplished by providing additional cutting means, such asedges, on the needle 44. In one embodiment, illustrated in FIG. 22 a,the needle has a primary cutting edge 92 that is rotatably attached tothe distal end of the needle 96. The primary cutting edge 92 puncturesthe fossa ovalis 72 when the needle 44 is advanced in the distaldirection. The distal end of the needle 44 is advanced into the leftatrium and the primary cutting edge 92 is rotated in the left atrium toexpose one or more additional cutting surface 94, such as by means of anaxially moveable pull-wire as disclosed elsewhere herein, or by otherappropriate remote control or biasing means as are well known to thoseordinary skill in the art. Retracting the needle back through the fossaovalis 72 in the proximal direction with the additional cutting surface94 in the exposed configuration, as illustrated in FIG. 22 b, results ina larger opening in the fossa ovalis 72.

In another embodiment, illustrated in FIG. 22 c, the needle 44 has twoor more primary cutting edges 92 that are attached to the needle 44 in ascissors-like configuration. The primary cutting edges 92 puncture thefossa ovalis when the needle 44 is advanced in the distal direction. Theprimary cutting edges 92 can be opened in the left atrium to expose oneor more additional cutting surfaces 94, such as by means of an axiallymoveable pull-wire as disclosed elsewhere herein, or by otherappropriate remote control or biasing means as are well known to thoseordinary skill in the art. Retracting the needle back through the fossaovalis 72 in the proximal direction with the additional cutting surfaces94 in the exposed configuration, as illustrated in FIG. 22 d, results ina larger opening in the fossa ovalis 72.

In another embodiment, illustrated in FIG. 22 e, the needle 44 has twoor more wings 90 that are contained within the needle 44 when the needle44 is advanced in the distal direction. The wings 90 are optionallybiased to expand when the needle 44 has crossed the fossa ovalis.Alternatively, the wings 90 are expanded from the proximal end of theneedle 44 such as by means of an axially moveable pull-wire as disclosedelsewhere herein, or by other appropriate remote control or biasingmeans as are well known to those ordinary skill in the art. Asillustrated in FIGS. 22 f and 22 g, expanding the wings 90 exposessecondary cutting surfaces 94. Retracting the needle back through thefossa ovalis 72 in the proximal direction with the additional cuttingsurfaces 94 in the exposed configuration results in a larger opening inthe fossa ovalis 72.

As illustrated in FIG. 22 f, the wings 90 may be configured withsecondary cutting surfaces 94 inclined at an angle extending toward theproximal end of the needle. Alternatively, as illustrated in FIG. 22 g,the wings 90 may be configured with rounded secondary cutting surfaces94. The wings 90 may also be inclined at an angle extending toward thedistal end of the needle or at an angle perpendicular to the axis of theneedle. As illustrated in FIG. 22H, in those embodiments where thesecondary cutting surfaces 94 are rounded or inclined at an angleextending toward the distal end of the needle, the wings 90 may bewithdrawn back into the needle 44 by advancing the needle 44 distallyinto the dilator 20.

Although certain embodiments incorporating secondary cutting surfaceshave been illustrated in conjunction with a dilator 20 as disclosedherein, one of ordinary skill in the art will appreciate that secondarycutting surfaces can be used with, or without, a dilator 20. The optimaltype of dilator, if any, to use with a needle having one or moresecondary cutting surfaces will depend on the particular application aswell as the design of the primary and secondary cutting surfaces, andcan be determined though routine experimentation.

In general, the cutting surfaces or other dilatation surfaces areadvanceable from a first, reduced crossing profile for advancement in afirst direction (e.g., distally through the fossa ovalis), and a second,enlarged crossing profile for movement in a second direction (e.g.,proximal retraction back through the fossa ovalis). Any of a variety ofstructures can be utilized, in which the cutting surface or tissueengagement surface is moveable from a first orientation in which itextend generally parallel to the longitudinal axis of the needle orother catheter component for penetration through a tissue surface, and asecond, inclined orientation with respect to the longitudinal axis topresent a larger cross sectional area. Such structures may be biased inthe direction of the second, enlarged crossing profile and restrained bya movable sheath, pull wire or other retention structure. Alternatively,the tissue engagement surface may be neutrally biased, and moved betweenthe reduced crossing profile and enlarged crossing profile orientationsby axial movement of a pull wire. As a further alternative, suchstructures may be advanced into the enlarged crossing profile byinflation of an underlying balloon in communication with the proximalend of the catheter by an axially extending inflation lumen.

As illustrated in FIG. 16A, the distal end 24 of dilator 20 is providedwith a tapered frustro conical surface 27. This allows the tubular body26 to function as a dilator, thereby permitting the tapered surface 27to enlarge the opening formed by needle 44 while minimizing “tenting” ofthe fossa ovalis during the transseptal access procedure. Alternatively,as illustrated in FIG. 16 b, the distal end 24 of dilator 20 may beprovided with a corkscrew or other helical structure 84, such as thosehaving threads with semi-circular or triangular cross-sections, therebypermitting the dilator to enlarge the opening formed by needle 44 byrotating while moving transversely through the opening. In yet anotherembodiment, illustrated in FIG. 16 c, the distal end 24 of dilator 20may be provided with one or more nozzles 86 capable of generating ahigh-pressure stream 88 of fluid, such as saline solution, therebyenlarging the opening formed by needle 44. Optionally, in all of theseembodiments, the dilator 20 may be transversely advanced while thedilator 20 is spinning or rotating with respect to the fossa ovalis.

Various embodiments of the present invention have been disclosed whereinthe needle 44 and dilator 20 have been described as separate structures.One of ordinary skill in the art will recognize that the needle anddilator need not be physically separate structures and will appreciatethat the allocation of particular features to the needle or dilator isillustrative only. For any particular application, the optimalallocation of the features disclosed herein as part of a single physicalstructure or physically part of either the needle or dilator will beapparent to one or ordinary skill in the through routineexperimentation.

In accordance with the method of the present invention, the right atriummay be initially accessed with a transseptal access system througheither the inferior or superior vena cava, which initially requirescannulation with an introducer sheath such as through the well known“Seldinger” technique. The transseptal access system of the presentinvention includes a transseptal sheath, a piercing dilator catheter 20as discussed above, and an appropriately sized guidewire.

Illustrated in FIG. 12 is an embodiment of an access sheath 74. Ingeneral, the sheath 74 comprises an elongate, flexible tubular bodyhaving preset bends as described below. In an unstressed configurationthe sheath 74 comprises a first substantially linear section 100, afirst curved section 110 and a second curved section 130. As usedherein, the term substantially linear also encompasses structures thatare actually linear. The first curved section 110 is distal to the firstsubstantially linear section 100, and the second curved section 130 isdistal to the first curved section 110. Preferably, there is a secondsubstantially linear section 120 between the first and second curvedsections, and a third substantially linear section 140 distal to thesecond curved section. In other embodiments the first curved section 110transitions directly into the second curved section 130 so there is nosecond substantially linear section 120, and in other embodiments thereis no third substantially linear section 140 distal to the second curvedsection.

In one embodiment, the sheath is designed to facilitate access to theleft atrium. In other embodiments, the sheath is designed to facilitateaccess to other physiological structures, such as the LAA, the orificeof the LAA, the distal aspect of the LAA, or pulmonary vein such as theleft superior pulmonary vein. One of ordinary skill in the art candetermine the optimum geometric orientation of the sheath for anyparticular application based on the desired region of access and theparticular patient's physiology through routine experimentation in viewof the disclosure herein. In one embodiment that is useful for accessingregions of the LAA, the first curved section is shaped to abut theinterior wall of the right atrium substantially opposite the fossaovalis while directing the distal tip toward the fossa ovalis. Thisfacilitates location of the fossa ovalis through tactile or othersensing means as described herein. The second curved section is shapedto facilitate location and access of the desired region of the LAA afterpenetration of the fossa ovalis. One of ordinary skill in the art willrecognize that the precise shape of these curves will depend on thepatient's physiology and can be determined through routineexperimentation.

The first and second curved sections may be provided in accordance withany of a variety of techniques. For example, the first and second curvedsections may be introduced prior to insertion of the sheath into thebody by bending the sheath, such as around a forming mandrel under heator in excess of the elastic limit of the sheath. Alternatively, aninjection molded sheath body may be provided with a predetermined bend,or by heat setting such as with removable flexible mandrels extendingthrough any interior lumen to maintain patency of the lumen around thebend. Alternatively, the first and second curved sections may be formedduring or after placement of the sheath in the patient. This may beaccomplished by providing the sheath with any of a variety of steeringmechanisms, which allow a distal portion of the sheath to be inclinedaway from the axis of the normal bias of the catheter. For example, oneor more axially moveable pull wires may extend through the length of thesheath. Proximal traction on a pull wire that is secured at a distallocation of the catheter will cause a lateral defection of the catheter.Other techniques will be known to those of skill in the art.

The geometric orientation of certain preferred embodiments that areuseful for accessing regions of the LAA are described below. As will beappreciated by one of ordinary skill in the art, depending on thepatient's physiology and the location to which access is sought, theobjects of the invention can be achieved by varying the geometric designof the sheath without departing from spirit of the invention. Inparticular the invention contemplates adding additional curved sectionsand/or by adding additional substantially linear sections.

In one embodiment, illustrated in FIG. 13, the point where the firstsubstantially linear section 100 begins to transition into the firstcurved section 110 defines a first proximal edge point A on the outsideedge of the exterior of the sheath. A tangent 200 to the outer edge ofthe first curved section 110 at the first proximal edge point A issubstantially parallel to the first substantially linear section 100.The point where the first curved section 110 begins to transition intothe second substantially linear section 120 defines a first distal edgepoint B on the outside edge of the exterior of the sheath. A tangent 210to the outer edge of the first curved section 110 at the first distaledge point B is substantially parallel to the second substantiallylinear section 120. In those embodiments where there is no secondsubstantially linear section 120 or where there are additional curved orsubstantially linear sections, the first distal edge point B is definedas the first inflection point distal to the first curved section 110 onthe outside edge of the exterior of the sheath. A tangent 210 to theouter edge of the first curved section 110 at the first distal edgepoint B is substantially parallel to the outside edge of the exterior ofthe sheath at point B.

The point where the second substantially linear section 120 begins totransition into the second curved section 130 defines a second proximaledge point C on the outside edge of the exterior of the sheath. Atangent 220 to the outer edge of the second curved section 130 at thesecond proximal edge point C is substantially parallel to the secondsubstantially linear section 120. In those embodiments where there is nosecond substantially linear section 120 or where there are additionalcurved or substantially linear sections, the second proximal edge pointC is defined as the first inflection point proximal to the second curvedsection 130. A tangent 220 to the outer edge of the second curvedsection 130 at the second proximal edge point C is substantiallyparallel to the outside edge of the exterior of the sheath at point C.

The point where the second curved section 130 begins to transition intothe third substantially linear section 140 defines a second distal edgepoint D on the outside edge of the exterior of the sheath. A tangent 230to the outer edge of the second curved section 130 at the second distaledge point D is substantially parallel to the third substantially linearsection 140. In those embodiments where there is no third substantiallylinear section 140 the second distal edge point D is defined as thedistal end point of the outside edge of the exterior of the sheath. Inthose embodiments where there are additional curved or substantiallylinear sections distal to the second curved section 140 the seconddistal edge point D is defined as the first inflection point distal tothe second curved section 130. A tangent 220 to the outer edge of thesecond curved section 130 at the first distal edge point B issubstantially parallel to the outside edge of the exterior of the sheathat point B.

The tangent 200 and the tangent 210 intersect to form an angle α. Theangle α is preferably about 90 degrees, generally between about 75degrees and about 105 degrees, and in other embodiments may be in therange of about 80 degrees to about 100 degrees. The tangent 220 and thetangent 230 intersect to form an angle β. The angle β is preferablyabout 90 degrees, generally between about 75 degrees and about 105degrees, and in other embodiments may be in the range of about 80degrees to about 100 degrees. The tangent 200 and the tangent 210 alsodefine a plane, 240. The tangent 220 and the tangent 230 also define aplane, 250. The plane 240 and the plane 250 define an angle γ. The angleγ is preferably about 90 degrees, generally between about 75 degrees andabout 105 degrees and in other embodiments may be in the range of about80 degrees to about 100 degrees.

The first curved section 110 has an arc length along the outside edge ofthe exterior of the sheath between point A and point B in the range ofabout 7.5 cm to about 9.5 cm. The second curved section 120 has an arclength along the outside edge of the exterior of the sheath betweenpoint C and point D in the range of about 5 cm to about 7.5 cm.

The sheath also defines a Cartesian coordinate system. The origin ofthis coordinate system is defined as point A. The X-axis is defined asparallel to tangent 200. The Y-axis is defined as the normal to tangent200 in plane 240. The Z-axis is defined as the normal to plane 240 atpoint A. In one embodiment, the distance along the Y-axis between pointA and point D is about 9 cm. In other embodiments, one of ordinary skillin the art will appreciate that the distance may vary depending upon thepatient's physiology, for example within the range of about 6 cm toabout 15 cm. In one embodiment, the distance along the Z-axis betweenpoint C and point D is about 3.5 cm. In other embodiments, one ofordinary skill in the art will appreciate that the distance may varydepending upon the patient's physiology, for example within the range ofabout 1 cm to about 6 cm.

In one embodiment, the first curved section 110 has a radius ofcurvature of about 5 cm. In other embodiments, one of ordinary skill inthe art will appreciate that the radius of curvature may vary dependingupon the patient's physiology, for example within the range of about 3cm to about 10 cm. In one embodiment, the second curved section 130 hasa radius of curvature of about 3 cm. In other embodiments, one ofordinary skill in the art will appreciate that the radius of curvaturemay vary depending upon the patient's physiology, for example within therange of about 1 cm to about 6 cm.

Preferably the sheath is sufficiently tourqueable that the location ofthe distal tip of the sheath can be controlled from the proximal end ofthe sheath. In one embodiment additional torquability is supplied byre-enforcing the shaft with stainless steel or high strength thinpolymeric braid. It is desirable to maximize the lubricity of the innersurface of the sheath to facilitate insertion and removal of variousdiagnostic and treatment devices within the sheath. In one embodimentthe inner surface of the sheath is coated with lubricity enhancingmaterial, such as PTFE.

Manageability and atraumaticity are facilitated by varying the stiffnessof the sheath along its length. It is desirable for the proximal sectionof the sheath to be relatively more stiff for torquability and kinkresistance, and for the distal section of the sheath to be relativelyless stiff. Generally, it is advantageous to soften the materialcomprising the sheath, and/or to make the wall of the sheath thinnertoward the distal end. In one embodiment, the proximal section of thesheath comprises 70D Pebax and has a wall thickness of about 0.015inches, the intermediate section of the sheath comprises 40D Pebax andhas a wall thickness of about 0.015 inches, and the distal section ofthe sheath comprises 40D Pebax and has a wall thickness of about 0.011inches. In one embodiment, the proximal section of the sheath extendsfor about 55 cm, the intermediate section of the sheath extends forabout 13 cm, and the distal section of the sheath extends for about 2cm. In other embodiments, the proximal section of the sheath may extendfrom about 40 cm to about 65 cm, the intermediate section of the sheathmay extend from about 5 cm to about 15 cm, and the distal section of thesheath may extend from about 2 mm to about 50 mm.

One of ordinary skill in the art will appreciate that the shaft may bemade of a greater or lesser number of sections having varyingcompositions and durometer hardnesses, that there may be gradual orabrupt transition between the sections, that the various sections maycomprise a variety of other materials, and that the thickness of thesheath wall may also be adjusted. The desired combination of theseparameters will depend on which parameters are selected and particularlyuseful combinations of these properties will be apparent to one ofordinary skill in the art through routine testing.

The atraumacity of the transition between the needle, dilator,transition catheter or the like may be enhanced by tapering the outerdiameter of the distal tip of the sheath and/or tapering the thicknessof the wall of the distal tip of the sheath. Visualization of the sheathcan be enhanced by marking the distal tip of the sheath a radiopaquemarker. One of ordinary skill in the art will appreciate that theradiopaque marker may be applied as a band, or in other shapes and atvarying distances from the distal tip.

The detrimental effect of drawing air into the catheter can be minimizedby providing grooves, vents or holes adjacent the distal end of thesheath. This prevents the creation of a vacuum during the withdrawal ofdevices from the sheath by allowing blood into the sheath even if thedistal opening of the sheath is in sealing contact with tissue. In oneembodiment, illustrated in FIG. 14 a, the vents 80 are slits in thedistal end of the sheath. In another embodiment, illustrated in FIG. 14b, the vents 80 are holes which extend transversely through the wallnear the distal end of the sheath. As illustrated in FIG. 14 c, the ventholes 80 may also be located within the radiopaque marker band to reduceor prevent collapsing or clogging of the vent holes.

In general, the vents 80 have a diameter or cross sectional areaequivalent to a round vent diameter within the range of from about 0.020inches to about 0.100 inches. Anywhere from about one to about ten ormore vents may be provided. In one embodiment, approximately 4 vents,each having a diameter of about 0.040 inches are provided. The vents maybe positioned in a single plane transverse to the longitudinal axis ofthe catheter as illustrated. The vents reside in a plane which isgenerally no more than about 5 mm from the distal end. Preferably, thevents are positioned within about 3 mm of the distal end of thecatheter. Alternatively, the vents may be staggered in two or moretransverse planes, depending upon the desired performancecharacteristics.

In present practice, the preferred access point is along the rightfemoral vein, although access from the left femoral vein is alsopossible. Access may also be achieved through a puncture in any of avariety of other veins of suitable internal diameter and the presentinvention is not limited in this regard.

A conventional spring tipped guide wire is thereafter advanced throughthe needle into the vein and the needle is subsequently removed. Thedilator 20 of the present invention is positioned within a sheath of thetype described herein, or other well-known sheaths, such as a 14 Frenchintroducer sheath. Subsequently, the sheath and inner dilator 20, incombination with the guide wire, are advanced through the femoral veinto the right atrium.

Referring to FIG. 4, there is illustrated a schematic cross-section of aportion of the heart 60. The right atrium 62 is communication with theinferior vena cava 64 and the superior vena cava 66. The right atrium 62is separated from the left atrium 68 by the intraatrial septum 70. Thefossa ovalis 72 is located on the intraatrial septum 70. As seen in FIG.4, the sheath 74 having the dilator 20 therein and a guidewire 76 havebeen positioned within the right atrium 62.

The guidewire 76 is thereafter distally advanced to access the superiorvena cava 66. See FIG. 5. The dilator 20 and sheath 74 are thereafteradvanced into the superior vena cava as illustrated schematically inFIG. 6. The guidewire 76 is proximally retracted.

When the sheath 74 and dilator 20 are in the superior vena cava and theguide wire has been removed, a transseptal needle 44 is advanced throughthe central lumen 39 of the dilator 20 and sheath 74. The transseptalneedle 44 is advanced (possibly with a stylet in place) to a point thatthe stylet tip is just inside the distal tip of the sheath 74 anddilator 20, a position previously noted by the operator, and the styletis withdrawn from the transseptal needle.

The remaining combination of the sheath 74 with the dilator 20 havingthe transseptal needle therein, is then drawn proximally from thesuperior vena cava while the first curved section 110 of the sheath,alone or in combination with the preset curve 25 at the distal region ofdilator 20, causes the tip of the sheath-dilator-transseptal needlecombination to “drag” along the wall of the right atrium and the septum70. Depending upon the particular embodiment of the transseptal accesssystem, some differences in the access method will occur at this point.

For example, in the reflected light embodiment disclosed in connectionwith FIGS. 1–3, the light source and detector 37 will likely need to becalibrated once the dilator 20 has been placed inside the right atrium62 but before the tip has been placed against the septum 70. The tip ofthe dilator 20 is then positioned against the septum 70 by distaladvancement through the sheath 74. The tip is then dragged along theseptum by proximal traction on the dilator 20 until the tip pops ontothe fossa 72. Once the tip is positioned on the fossa 72, thecharacteristic color at the fossa is detected by the detector 37. Aresponsive audio or visual signal is generated, confirming that thecatheter 20 is now properly positioned at the fossa ovalis 72.

The physician is normally assisted during placement, as in the entireprocedure, by fluoroscopy or other visualization techniques. To assistin such visualization, the distal tip of sheath 74 and the distal tip ofdilator 20 may be provided with a radiopaque marker. In addition, somephysicians find it desirable to infuse a radiopaque dye through thetransseptal needle at various stages of the procedure to assist invisualization, particularly following the transseptal puncture.

After the tip of the sheath-dilator-transseptal needle combination hasbeen placed in the desired location against the fossa ovalis 72, thetransseptal needle 44 is abruptly advanced to accomplish a quickpuncture. See FIG. 8. In one embodiment the needle is advanced byapplying a force to the proximal end of the needle. In this embodimentthe needle often comprises a stiff proximal section and a flexibledistal section. The distal section preferably comprises ribbon coil.Alternatively, as illustrated in FIG. 20 a, the needle 44 is loaded intoneedle cavity 89 against a distal advancement biasing means 85, such asa spring or coil. The needle 44 is held against the biasing means 85 bya release lock 87. The release lock 87 may comprise any commonly usedretaining means, such as corresponding inward and outward projections,grooves or flanges on the needle cavity 89 and the needle 44. The distalend of the sheath 74 is placed in the desired location against the fossaovalis 72. As illustrated in FIG. 20 b, the release lock 87 is openedand the biasing means rapidly advances the needle 44 through the fossaovalis 72. Immediately after the puncture, one medical technique is toconfirm the presence of the tip 50 of the transseptal needle 44 withinthe left atrium 68. Confirmation of such location of the tip 50 of thetransseptal needle 44 may be accomplished by monitoring the pressuresensed through the transseptal needle lumen to ensure that the measuredpressure is within the expected range and has a waveform configurationtypical of left atrial pressure. Alternatively, proper position withinthe left atrium 68 may be confirmed by analysis of oxygen saturationlevel of the blood drawn through the transseptal needle 44; i.e.,aspirating fully oxygenated blood. Finally, visualization throughfluoroscopy alone, or in combination with the use of dye, may also serveto confirm the presence of the tip 50 of the transseptal needle 44 inthe left atrium 68.

After placing the transseptal needle tip 50 within the left atrium 68,the tip 27 of the dilator 20 is advanced through the septum 70 and intothe left atrium 68. Typically, care is taken to ensure that, at the sametime of advancing the dilator and sheath tip into the left atrium, thetip of the transseptal needle is not advanced a sufficient distance thatthe needle 44 can damage the opposing wall of the left atrium 68. Whenthe tapered tip 27 of dilator 20 appears to have entered the left atrium68, the transseptal needle 44 is withdrawn. The sheath 74 is thenadvanced into the left atrium 68, either by advancing the sheath 74alone over the dilator 20 or by advancing the sheath 74 and dilator 20in combination. See FIG. 10. The dilator 20 is then withdrawn fromsheath 74 when the latter has been advanced into the left atrium, thusleaving the main lumen of sheath 74 as a clear pathway to advancingfurther diagnostic or therapeutic instruments into the left atrium.

During the initial puncture of the fossa ovalis and the subsequentadvancement of the dilator 20 and sheath 74 into the left atrium, it isdesirable to minimize “tenting” of the fossa ovalis. The needle 44 isoptionally coated with a lubricous material, often a material such asPTFE, hydrophilic material or parylene, preferably PTFE. The dilator 20is also optionally coated with a lubricous material, often a materialsuch as PTFE, hydrophilic material or parylene, preferably PTFE.

In one embodiment, illustrated in FIGS. 15 a–15 c, the sheath 74contains an inflatable balloon 77 at the distal end and means forinflating the balloon 75, such as an inflation lumen. The balloon 77 isin a deflated position as the needle 44 crosses the fossa ovalis. In oneembodiment, illustrated in FIG. 15 b, the balloon 77 is disposed aroundthe needle 44, and the balloon 77 is inflated as it crosses the fossaovalis, thereby enlarging the puncture made by the needle 44. Thisembodiment may be used with or without an additional dilator 20 asdescribed herein. If desired, the balloon 77 may be deflated andwithdrawn after the sheath 74 has accessed the left atrium.Alternatively, the balloon may be left inflated, or further inflatedafter the sheath 74 accesses the left atrium. In another embodiment, asillustrated in FIG. 15 c, the balloon 77 may be inflated after theballoon crosses the fossa ovalis. In those embodiments where the balloon77 remains in an inflated position after the sheath 74 crosses the fossaovalis, the inflated balloon 77 creates an atraumatic distal tip thatcan be navigated to access a location of interest, such as the LAA. Inthose embodiments where the balloon 77 is inflated to a diameter greaterthan the diameter of the sheath 74, the balloon prevents the sheath fromunintentionally passing back through the fossa ovalis during subsequentprocedures.

In another embodiment, illustrated in FIGS. 17A, at least a portion ofthe needle 44, the dilator 20 and at least a distal portion of thesheath 74 are encompassed by a thin-walled jacket 82 that is made oflubricous material, preferably PTFE. As illustrated in FIG. 17B, thedistal end of the jacket 82 advances across the fossa ovalis 72 with theneedle 44. As illustrated in FIG. 17C, the dilator 20 and sheath 74 thencross the fossa ovalis 72 within the jacket 82. Preferably the jacket isradially enlargeable and may have a thickness in the range of about 0.05mm to about 0.75 mm depending upon the construction material. Theoptimum material or combination of materials for coating the needle 44,coating the dilator 20, or forming the jacket 82 can be determined forany particular application through routine experimentation by one orordinary skill in the art based on the disclosures herein.

In another embodiment, illustrated in FIG. 18, the sheath 74 is itselftapered at its distal end to encompass at least a portion of thedilator. In this embodiment the sheath 74 is preferably tapered toencompass the dilator and at least a portion of the needle 44. Inanother embodiment, illustrated in FIG. 19, the sheath 74 includesmeans, such as a vacuum lumen, for applying a vacuum 83 at the distalend. The vacuum lumen may be concentrically disposed within the needle44 and the dilator 20, concentrically disposed within the dilator 20,but side by side with the needle 44, or side by side with the dilator20. In one embodiment the vacuum is applied to the fossa ovalis beforethe needle 44 punctures the fossa ovalis. Alternatively, the vacuum isapplied to the fossa ovalis after the needle punctures the fossa ovalisand before or as the dilator 20 crosses the fossa ovalis. The vacuummaintains the position of the fossa ovalis and reduces “tenting” duringthe transseptal access procedure. Alternatively the vacuum may draw thefossa ovalis into the sheath 74. In yet another embodiment, which one orordinary skill in the art will appreciate may be used in conjunctionwith many of the embodiments described above, the needle 44 isoscillated at ultrasonic frequencies to further reduce friction betweenthe needle 44 and the fossa ovalis 72.

Although the present invention has been described in terms of certainpreferred embodiments, other embodiments will become apparent to thoseof skill in the art in view of the disclosure herein. Accordingly, thescope of the present invention is not intended to be limited by thespecific embodiments disclosed herein, but, rather, by the full scope ofthe claims attached below.

1. A transseptal access system, comprising a sheath, a dilator and a needle; wherein the sheath comprises: a first curved section shaped to abut the interior wall of the right atrium substantially opposite the septum and directed toward the septum, and a second curved section shaped to direct a distal end of the sheath toward the left atrial appendage; the first curved section having an outer edge that defines a first proximal edge point, and a first distal edge point wherein the intersection between a tangent drawn to the first curved section at the first proximal edge point and a tangent drawn to the first curved section at the first distal edge point, define a first angle and a first plane; the second curved section having an outer edge that defines a second proximal edge point, and a second distal edge point wherein the intersection between a tangent drawn to the second curved section at the second proximal edge point and a tangent drawn to the second curved section at the second distal edge point, define a second angle and a second plane; wherein the first angle is within the range of about 75 degrees to about 105 degrees; wherein the second angle is within the range of about 75 degrees to about 105 degrees; wherein the angle between the first and second plane is within the range of about 75 degrees to about 105 degrees; wherein the needle is coated with PTFE.
 2. The transseptal access system of claim 1, wherein the first angle is within the range of about 80 degrees to about 100 degrees.
 3. The transseptal access system of claim 1, wherein the second angle is within the range of about 80 degrees to about 100 degrees.
 4. The transseptal access system of claim 1, wherein the dilator comprises an inflatable balloon.
 5. The transseptal access system of claim 1, wherein the dilator comprises a spiral helical structure.
 6. The transseptal access system of claim 1, wherein the dilator is coated with PTFE.
 7. The transseptal access system of claim 1, wherein the needle is advanced by a biasing means.
 8. A transseptal access system, comprising a sheath, a dilator and a needle; wherein the sheath comprises: a first curved section shaped to abut the interior wall of the right atrium substantially opposite the septum and directed toward the septum, and a second curved section shaped to direct a distal end of the sheath toward the left atrial appendage; the first curved section having an outer edge that defines a first proximal edge point, and a first distal edge point wherein the intersection between a tangent drawn to the first curved section at the first proximal edge point and a tangent drawn to the first curved section at the first distal edge point, define a first angle and a first plane; the second curved section having an outer edge that defines a second proximal edge point, and a second distal edge point wherein the intersection between a tangent drawn to the second curved section at the second proximal edge point and a tangent drawn to the second curved section at the second distal edge point, define a second angle and a second plane; wherein the first angle is within the range of about 75 degrees to about 105 degrees; wherein the second angle is within the range of about 75 degrees to about 105 degrees; wherein the angle between the first and second plane is within the range of about 75 degrees to about 105 degrees; wherein the dilator comprises a vacuum lumen to allow application of a vacuum to the fossa ovalis.
 9. The transseptal access system of claim 8, wherein the first angle is within the range of about 80 degrees to about 100 degrees.
 10. The transseptal access system of claim 8, wherein the second angle is within the range of about 80 degrees to about 100 degrees.
 11. A transseptal access system, comprising a sheath, a dilator and a needle; wherein the sheath comprises: a first curved section shaped to abut the interior wall of the right atrium substantially opposite the septum and directed toward the septum, and a second curved section shaped to direct a distal end of the sheath toward the left atrial appendage; the first curved section having an outer edge that defines a first proximal edge point, and a first distal edge point wherein the intersection between a tangent drawn to the first curved section at the first proximal edge point and a tangent drawn to the first curved section at the first distal edge point, define a first angle and a first plane; the second curved section having an outer edge that defines a second proximal edge point, and a second distal edge point wherein the intersection between a tangent drawn to the second curved section at the second proximal edge point and a tangent drawn to the second curved section at the second distal edge point, define a second angle and a second plane; wherein the first angle is within the range of about 75 degrees to about 105 degrees; wherein the second angle is within the range of about 75 degrees to about 105 degrees; wherein the angle between the first and second plane is within the range of about 75 degrees to about 105 degrees; wherein the dilator includes at least one infusion port for infusing saline solution.
 12. The transseptal access system of claim 11, wherein the first angle is within the range of about 80 degrees to about 100 degrees.
 13. The transseptal access system of claim 11, wherein the second angle is within the range of about 80 degrees to about 100 degrees.
 14. The transseptal access system of claim 11, wherein the dilator is coated with PTFE.
 15. The transseptal access system of claim 11, wherein the needle is advanced by a biasing means.
 16. A transseptal access system, comprising a sheath, a dilator and a needle; wherein the sheath comprises: a first curved section shaped to abut the interior wall of the right atrium substantially opposite the septum and directed toward the septum, and a second curved section shaped to direct a distal end of the sheath toward the left atrial appendage; the first curved section having an outer edge that defines a first proximal edge point, and a first distal edge point wherein the intersection between a tangent drawn to the first curved section at the first proximal edge point and a tangent drawn to the first curved section at the first distal edge point, define a first angle and a first plane; the second curved section having an outer edge that defines a second proximal edge point, and a second distal edge point wherein the intersection between a tangent drawn to the second curved section at the second proximal edge point and a tangent drawn to the second curved section at the second distal edge point, define a second angle and a second plane; wherein the first angle is within the range of about 75 degrees to about 105 degrees; wherein the second angle is within the range of about 75 degrees to about 105 degrees; wherein the angle between the first and second plane is within the range of about 75 degrees to about 105 degrees; wherein the sheath comprises a vacuum lumen to allow application of a vacuum to the fossa ovalis.
 17. The transseptal access system of claim 16, wherein the first angle is within the range of about 80 degrees to about 100 degrees.
 18. The transseptal access system of claim 16, wherein the second angle is within the range of about 80 degrees to about 100 degrees.
 19. A transseptal access system, comprising a sheath, a dilator and a needle; wherein the sheath comprises: a first curved section shaped to abut the interior wall of the right atrium substantially opposite the septum and directed toward the septum, and a second curved section shaped to direct a distal end of the sheath toward the left atrial appendage; the first curved section having an outer edge that defines a first proximal edge point, and a first distal edge point wherein the intersection between a tangent drawn to the first curved section at the first proximal edge point and a tangent drawn to the first curved section at the first distal edge point, define a first angle and a first plane; the second curved section having an outer edge that defines a second proximal edge point, and a second distal edge point wherein the intersection between a tangent drawn to the second curved section at the second proximal edge point and a tangent drawn to the second curved section at the second distal edge point, define a second angle and a second plane; wherein the first angle is within the range of about 75 degrees to about 105 degrees; wherein the second angle is within the range of about 75 degrees to about 105 degrees; wherein the angle between the first and second plane is within the range of about 75 degrees to about 105 degrees; wherein the needle has a spiral helical structure.
 20. The transseptal access system of claim 19, wherein the first angle is within the range of about 80 degrees to about 100 degrees.
 21. The transseptal access system of claim 19, wherein the second angle is within the range of about 80 degrees to about 100 degrees.
 22. A transseptal access system comprising a sheath, a dilator and a needle; wherein the sheath comprises: a first curved section shaped to abut the interior wall of the right atrium substantially opposite the septum and directed toward the septum, and a second curved section shaped to direct a distal end of the sheath toward the left atrial appendage; the first curved section having an outer edge that defines a first proximal edge point, and a first distal edge point wherein the intersection between a tangent drawn to the first curved section at the first proximal edge point and a tangent drawn to the first curved section at the first distal edge point, define a first angle and a first plane; the second curved section having an outer edge that defines a second proximal edge point, and a second distal edge point wherein the intersection between a tangent drawn to the second curved section at the second proximal edge point and a tangent drawn to the second curved section at the second distal edge point, define a second angle and a second plane; wherein the first angle is within the range of about 75 degrees to about 105 degrees; wherein the second angle is within the range of about 75 degrees to about 105 degrees; wherein the angle between the first and second plane is within the range of about 75 degrees to about 105 degrees; and an ultrasound transducer for oscillating the needle at ultrasonic frequencies.
 23. The transseptal access system of claim 22, wherein the first angle is within the range of about 80 degrees to about 100 degrees.
 24. The transseptal access system of claim 22, wherein the second angle is within the range of about 80 degrees to about 100 degrees.
 25. A transseptal access system, comprising a sheath, a dilator and a needle; wherein the sheath comprises: a first curved section shaped to abut the interior wall of the right atrium substantially opposite the septum and directed toward the septum, and a second curved section shaped to direct a distal end of the sheath toward the left atrial appendage; the first curved section having an outer edge that defines a first proximal edge point, and a first distal edge point wherein the intersection between a tangent drawn to the first curved section at the first proximal edge point and a tangent drawn to the first curved section at the first distal edge point, define a first angle and a first plane; the second curved section having an outer edge that defines a second proximal edge point, and a second distal edge point wherein the intersection between a tangent drawn to the second curved section at the second proximal edge point and a tangent drawn to the second curved section at the second distal edge point, define a second angle and a second plane; wherein the first angle is within the range of about 75 degrees to about 105 degrees; wherein the second angle is within the range of about 75 degrees to about 105 degrees; wherein the angle between the first and second plane is within the range of about 75 degrees to about 105 degrees; wherein the needle has at least one expandable cutting surface.
 26. The transseptal access system of claim 25, wherein the first angle is within the range of about 80 degrees to about 100 degrees.
 27. The transseptal access system of claim 25, wherein the second angle is within the range of about 80 degrees to about 100 degrees. 